1. Field of the Invention
The present invention relates to a submergible, underwater well completion habitat and a method of employing the same in the completion of wells at extended depths. More particularly, the invention refers to a well completion habitat which may be attached to an underwater well platform and maintained at a pressure of sufficient value to expel sea water from the work chamber and also to maintain it substantially water free so that one or more saturated divers may work within the habitat to complete the well.
2. The Prior Art
Methods for completing oil and gas wells at depths greater than 200 feet have been the subject of much research and development for many years. Remote control devices have been developed which may be operated from specially equipped ships and barges. However, these systems are complicated and require precise control of automatic devices that may be resting on or near the ocean floor many hundreds of feet below their control vessel.
To avoid the use of remote control devices, much effort has been invested in perfecting underwater work apparatus that permit oilfield specialists to work in a one atmosphere environment. A subsea structure or chamber has been provided that will permit normal breathing and which is sealed from the surrounding ocean. Such a structure is described and claimed in U.S. Pat. No. 3,656,549 to Holbert et al.
In all of these subsea work chambers, there are two requirements which must be met. First, the chamber must be capable of withstanding full hydrostatic pressure of the sea water acting on its exterior while only one atmosphere of pressure acts on its interior. Second, an effective seal must be provided to close the chamber and this seal, like the walls of the chamber, is subjected to the differential pressure which exists between the exterior and the interior of the chamber.
Justification for such one atmosphere subsea chambers is based upon a desire to utilize "oil field" trained workers at the well head, as opposed to "divers" who normally work at these depths but who are not normally trained in oilfield practices. Disadvantages to divers working underwater are their positive buoyancy, restricted maneuverability and visual limitations caused by lack of light and by light blocking or reflecting particles suspended in their water environment.
There are many patents illustrating apparatus which provide an air tight, water-free work environment at an underwater well structure. One of the most recent is U.S. Pat. No. 4,004,635 to R.A.M. Marquarie et al., which describes a bell housing assembly for connecting inflexible pipe onto a well head. However, this chamber, too, is water tight and is designed for one atmosphere operation.
U.S. Pat. No. 3,513,910, to Robert D. Townsend, describes a subsea production satellite having the requirement of a water free chamber capable of sustaining a one atmosphere environment while withstanding the hydrostatic forces surrounding the vessel.
It is an object of this invention to provide an underwater well completion system that will allow one or more saturated divers to complete an underwater well while working in a water free environment.
It is a further object to provide an underwater well completion habitat that can be lowered from the surface of the ocean and attached to an underwater well structure or otherwise disposed in proper position.
It is a still further object of this invention to provide an underwater well completion habitat that can be attached to an underwater well structure in which pressure is of sufficient value to expel water therefrom and also to maintain the chamber substantially water free.
It is another object of this invention to provide an underwater well completion habitat, which when attached to an underwater well structure, provides a water free work environment and a breathable atmosphere therein.
Another object of this invention is to provide an underwater well completion habitat that does not have to withstand the full hydrostatic pressure of the water exterior thereof with only atmosphere pressure therein.
An additional object of this invention is to provide an underwater well completion habitat constructed of materials which will withstand impinging water current forces, when in a fixed position in a body of water.
Another object of this invention is to provide an underwater well completion habitat whose internal pressure when disposed below the surface will be substantially equal to the hydrostatic pressure of the surrounding water.
A still further object is to provide an underwater well completion habitat wherein saturated divers may complete and test an underwater well with equipment, pumps, flow lines and the like which have been carried to the well structure within and attached to the completion habitat.